The electronic radio frequency identification (RFID) systems are finding increasingly widespread applications.
In practice, these systems are already today widely used to identify, locate or track objects, animals or people (access cards; toll; electronic passport etc.).
It generally concerns a reader and a transponder incorporated, for example, in a support such as a tag or a card. In the present invention, reference is equally made to the remotely powered transponders, that is to say transponders that do not have their own energy source to transmit data, and transponders that have their own energy source, but which, should the latter fail or for certain applications, can operate, for example, in degraded mode, as a remotely powered transponder.
The reader, considered as a base station, generates a carrier wave (short range alternating magnetic field) which serves to power the contactless cards in proximity to the antenna of the reader. This is referred to as remote power feed. Furthermore, this carrier wave supplies a clock to the card for the operation of its various blocks. Finally, it serves as a support for the reader—card and card—reader communications.
In the exchange of information between the base station and the transponder, a distinction is drawn between the pathway from the reader to the card (the base station has a transmitter function) and the pathway from the card to the reader (the base station has a receiver function).
This exchange is subject to the constraints/provisions set out, for example, in the ISO14443 Standard which defines, among other things, the type of modulation and of coding as well as the bit rate of the transactions between a reader and a contactless card. This bit rate is currently between 106 and 848 kb/s.
Proposals are currently being formulated to extend this bit rate beyond the Mb/s.
To be accepted, these extensions have to be as compatible as possible with the current standard. In practice, the manufacturers want a minimum of modifications to the base of readers already installed.
Another constraint relates to the magnetic field emissions which have to comply with the European recommendations ERC-70-03 and/or ETS 300-330.